Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 2 - Section 2.1 - Complex Numbers - Exercise Set - Page 314: 47

Answer

The solution of the equation $4{{x}^{2}}+8x+13=0$ in standard form is $\left\{ -1+\frac{3}{2}i,-1-\frac{3}{2}i \right\}$.

Work Step by Step

Consider the equation,$4{{x}^{2}}+8x+13=0$ Compare the equation $4{{x}^{2}}+8x+13=0$ with $a{{x}^{2}}+bx+c$. $\begin{align} & a=4 \\ & b=8 \\ & c=13 \end{align}$ Substitute $a=4$, $b=8$ and $c=13$ in the formula $x=\frac{-b\pm \sqrt{{{b}^{2}}-4ac}}{2a}$. $\begin{align} & x=\frac{-8\pm \sqrt{{{8}^{2}}-4\left( 4 \right)\left( 13 \right)}}{2\left( 4 \right)} \\ & =\frac{-8\pm \sqrt{64-208}}{8} \\ & =\frac{-8\pm \sqrt{-144}}{8} \end{align}$ Use the property $\sqrt{-b}=i\sqrt{b}$. \[\begin{align} & x=\frac{-8\pm i\sqrt{144}}{8} \\ & =\frac{-8\pm 12i}{8} \\ & =\frac{-8}{8}\pm \frac{12}{8}i \\ & =-1\pm \frac{3}{2}i \end{align}\] Therefore, the solution of the equation $4{{x}^{2}}+8x+13=0$ in standard form is $\left\{ -1+\frac{3}{2}i,-1-\frac{3}{2}i \right\}$.
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